Chickenpox and Shingles in Minnesota 2014
Since Jan. 1, 2013, all cases of chickenpox are required to be reported. This report is based on case
reports provided by medical providers, child care providers, and schools.
Chickenpox (Varicella) Case Reporting, January to December 2014
In 2014, MDH received reports of 559 suspected cases of chickenpox, of which 297 were identified as
probable and confirmed cases and used for statistics. Minnesota had a statewide annual incidence of 6
cases/100,000 population, which is similar to the most recent available national statistic of 5.3/100,000
(2012). Age information was available for all Minnesota cases.
Varicella Cases and Incidence Rate by Age Group,
Minnesota 2014 (N=297)
Incidence per 100000
50
50.0
45
45.0
40
40.0
35
35.0
30
30.0
25
25.0
20
20.0
15
15.0
10
10.0
5
5.0
Incidence
Number of Cases
Number of Cases
0.0
0
<1
1-2
3-4
5-6
7-8
9-10
11-12
13-14
15-16
17-18
19+
Ages in Years
This graph shows the number of cases by age in years and by age incidence. Incidence peaked in children
<1 year. Children in this age group are too young to be vaccinated for varicella. Incidence declined in
each succeeding age group and was lowest in adults aged 19 and over.
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Chickenpox and Shingles in Minnesota 2014
Minnesota Varicella Cases by County, January 1 –December 31, 2014
County
Cases
County
Cases
County
Cases
County
Cases
Anoka
27
Goodhue
4
Olmsted
12
Stearns
2
Becker
1
Hennepin
71
Otter Tail
4
Steele
2
Blue Earth
2
Houston
2
Pine
1
Traverse
1
Carver
4
Hubbard
2
Ramsey
35
Wabasha
4
Chisago
7
Isanti
3
Redwood
1
Wadena
1
Clay
1
Kanabec
1
Renville
1
Waseca
2
Clearwater
1
Kandiyohi
2
Rice
9
Washington
15
Crow Wing
3
Martin
1
Rock
2
Watonwan
6
Dakota
19
Mille Lacs
1
St. Louis
4
Winona
3
Dodge
3
Morrison
1
Scott
16
Wright
10
Freeborn
2
Nobles
1
Sherburne
7
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Chickenpox and Shingles in Minnesota 2014
Chickenpox (Varicella) School Reporting 2014-15
Because school outbreaks have declined steeply, schools are asked to report all suspect or confirmed
cases as they occur. However, outbreaks are still reportable. During the 2014-15 school year:
•
•
•
Only one Minnesota school reported an outbreak of five or more verifiable cases.
10 students and no staff were cases.
Only one outbreak case had been vaccinated for varicella.
Reported Chickenpox (Varicella) Outbreaks in
Minnesota Schools and Number of Students Involved,
by School Year
No. of Outbreaks
1400
80
1200
70
60
1000
50
800
40
600
Number of Outbreaks
Number of Cases
No. of Cases
30
400
20
200
10
0
0
2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15
This graph shows that outbreaks of chickenpox in Minnesota schools have sharply declined since
requirements for one dose (2004) and two doses (2009) of chickenpox vaccine were put into place.
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Chickenpox and Shingles in Minnesota 2014
Schools have been reporting individual cases of chickenpox since the 2012-13 school year. Cases that are
not related to an outbreak of five or more are called sporadic cases. High levels of vaccination in a school
help to prevent outbreaks by limiting the spread of disease to others. For the first three years of individual
case reporting, the total number of sporadic, probable and confirmed cases reported in Minnesota school
children are:
•
•
•
2012-13: 175
2013-14: 99
2014-15: 139
Confirmed Chickenpox Cases by Rash Severity and
Vaccination Status, Minnesota, 2014, N=95
Number of Cases
60
50
40
Vaccinated, >2 Doses
30
Vaccinated, 1 Dose
20
Unvaccinated
10
0
Mild (<50)
Mild/Mod. (50-249) Moderate (250-499)
Severe (>500)
Disease Severity (Number of Lesions)
Varicella vaccine prevents most cases of chickenpox. If breakthrough disease does occur, symptoms are
usually mild, with fewer lesions. Cases with severe rash are more likely to have lesions in the mouth and
throat, which can make swallowing uncomfortable and increase the risk of dehydration. This graph shows
that severe disease was not seen in vaccinated individuals in 2014. Those vaccinated individuals who got
breakthrough chickenpox got mild or mild-to-moderate disease.
Cases hospitalized with chickenpox also provided evidence for vaccine effectiveness. During 2014, 12
individuals were hospitalized because of varicella, but there were no reported deaths. Seven of the cases
had complications of varicella, such as bacterial superinfection, high fever, seizures, and dehydration.
Eight of the cases (67%) had never received varicella-containing vaccine. Three cases (25%) were partly
vaccinated (1 dose) and were hospitalized for observation rather than for complications or severe rash.
The remaining case had an unknown history of vaccination.
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Chickenpox and Shingles in Minnesota 2014
Shingles (Zoster) in Minnesota Children Under 18 Years of Age
From the 2006-07 through the 2012-13 school years, MDH conducted surveillance for shingles in
children chiefly through reports from schools. As increasing numbers of children were being vaccinated
for chickenpox, cases of shingles being reported from K-12 schools declined from 15.7/100,000 to
9.4/100,000. Since that time, MDH has begun receiving reports from health care providers and child care
as well. Even so, the total number of case reports per calendar year from all sources remains lower than
the numbers formerly reported by schools alone.
160
18
140
16
14
Total Cases
120
12
100
10
80
8
60
6
40
Cases per 100,000
Zoster (Shingles) Cases in Minnesota Schools
4
20
2
0
0
2006-07
2007-08
2008-09
2009-10
School Year
2010-11
2011-12
2012-13
Total Cases
For more information on shingles in Minnesota, see the “Varicella and Zoster” articles in the Disease
Control Newsletter www.health.state.mn.us/divs/idepc/newsletters/dcn/sum14/varicella.html.
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